A calibrator or sizer for imparting the final dimensions to a length of siding can comprise an upper portion, a lower portion connectable to the upper portion and a gap formed between them and into which the length of extruded material can be received.
The calibrator (see, for example, German patent document DE-AS No. 22 18 557) had a lower portion on which the upper portion sits and after centering could be screwed and/or pinned or otherwise brought together. The opening and closing of this calibrator thus requires considerable time and work. Additionally there is danger of clamping or pinching the extruded material and/or of otherwise causing defects to occur. These disadvantages are not essentially changed when the upper and lower portion are pivotally connected to each other by a pivot bearing.
The calibrator is usually cooled with water. This can circulate in a cooling jacket positioned around the calibrator tube. It flows in the water jacket turbulently and generally in the extrusion direction (Austrian Patent No. 322 824). Water can also be conducted in longitudinal passages which run in the extrusion direction; however since in this case different spacings of these passages are required to effect different cooling of the extrudate it leads to increased surface stresses in the extrusion and to reduced output.